Séminaires : Séminaire de Topologie

Equipe(s) : tga,
Responsables :Najib Idrissi et Emmanuel Wagner
Email des responsables : najib.idrissi-kaitouni@u-paris.fr, emmanuel.wagner@imj-prg.fr
Salle : 1013
Adresse :Sophie Germain
Description

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Orateur(s) Lukas Lewark - Université de Berne,
Titre Unknotting and Surfaces
Date16/04/2019
Horaire10:30 à 11:30
Diffusion
RésumeThe unknotting number of a knot is the minimum number of crossing changes necessary to make the knot trivial. This is at the same time one of the most intuitive and one of the most inaccessible knot invariants. We'll discuss a variation thereof: the minimum number n such that the knot can be transformed into a knot with trivial Alexander polynomial by n positive and n negative crossing changes. We'll see three equivalent characterizations of this knot invariant: in terms of the Blanchfield pairing, and in terms of the minimal genus of certain surfaces in 3-space, and in 4-space. The talk is based on joint work with Peter Feller.
Salle1013
AdresseSophie Germain
© IMJ-PRG